The long range objective of the proposed research is to understand the contribution of the activity of single cells in visual cortex to the visual behavior of animals and man. As a means of approaching this goal, electrophysiological data gathered from infrahuman animals will be compared and correlated with human and animal psychophysical measures. Thus, the proposed experiments are designed to link data obtained from single cells of cat visual cortex with related psychophysical data derived from both humans and cats. The series of experiments proposed are: 1) behavioral determination of the tuning characteristics of orientation selective channels in the cat visual system; 2) electrophysiological studies of habituation and masking of orientation selective cells in the visual cortex of the cat and; 3) psychophysical study of the orientation selectivity of different size-tuned channels in human vision. BIBLIOGRAPHIC REFERENCES: Cat Visual psychophysics: Neural correlates and comparisons with man. Berkley, M. A. in Sprague, J. and Epstein, A. (eds.) Progress in physiological psychology. Academic press, 1976 (In the press.) The role of geniculo-cortical system in form vision: Areas 17 and 18 and visual acuity in the cat. Berkley, M. A. Sprague, J., and Bloom, Marie, ARVO, Sarasota, 1976.